Abstract
BackgroundSwitchgrass (Panicum virgatum L.) is a dedicated lignocellulosic feedstock for bioenergy production. The SQUAMOSA PROMOTER-BINDING PROTEIN (SBP-box)-LIKE transcription factors (SPLs) change plant architecture and vegetative-to-reproductive phase transition significantly, and as such, they are promising candidates for genetic improvement of switchgrass biomass yield. However, the genome-wide identification and functional characterization of SPL genes have yet to be investigated in herbaceous energy crops.ResultsWe identified 35 full-length SPL genes in the switchgrass genome. The phylogenetic relationship and expression pattern of PvSPLs provided baseline information for their function characterization. Based on the global overview of PvSPLs, we explored the biological function of miR156-targeted PvSPL1 and PvSPL2, which are closely related members of SPL family in switchgrass. Our results showed that PvSPL1 and PvSPL2 acted redundantly to modulate side tiller initiation, whereas they did not affect phase transition and internode initiation. Consistently, overexpression of the miR156-resistant rPvSPL2 in the miR156-overexpressing transgenic plants greatly reduced tiller initiation, but did not rescue the delayed flowering and increased internode numbers. Furthermore, suppression of PvSPL2 activity in switchgrass increased biomass yield and reduced lignin accumulation, which thereby elevated the total amount of solubilized sugars.ConclusionsOur results indicate that different miR156-targeted PvSPL subfamily genes function predominantly in certain biological processes in switchgrass. We suggest that PvSPL2 and its paralogs can be utilized as the valuable targets in molecular breeding of energy crops for developing novel germplasms with high biofuel production.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0516-z) contains supplementary material, which is available to authorized users.
Highlights
Switchgrass (Panicum virgatum L.) is a dedicated lignocellulosic feedstock for bioenergy production
These results suggest that SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL) are a group of functionally diverse transcription factors, which is consistent with SPLs representing a structurally heterogeneous family
Genome‐wide identification, phylogenetic relationship, and chromosomal distribution of PvSPLs Based on the Hidden Markov Model profile of conserved SQUAMOSA PROMOTER-BINDING PROTEIN (SBP) domain (PF03110) sequence, 35 SPL family members, designated as PvSPL1 to PvSPL35, were identified in the switchgrass genome using the Blastp and tBlastn programs
Summary
Switchgrass (Panicum virgatum L.) is a dedicated lignocellulosic feedstock for bioenergy production. Other studies indicate that SPLs participate in copper homeostasis, cytokinin response, and the biosynthesis of anthocyanin, terpene, carotenoid, and lignin [14,15,16,17,18,19] These results suggest that SPLs are a group of functionally diverse transcription factors, which is consistent with SPLs representing a structurally heterogeneous family. The reduction in transcript abundance of these SPLs accompanying with the alteration of morphological characterization depends on the level of miR156 in the transgenic switchgrass plants. These results suggest that it is required to maintain the expression of different SPL genes at appropriate levels in vivo for plant normal development and healthy growth
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